Armour

ABSTRACT

An armour comprising a composite material consisting of a mixture of hard particulate material and fibrous material dispersed throughout a matrix material, the distribution of the particulate and fibrous materials through the matrix material being such that the properties of the composite material change progressively from predominantly hard at one surface to predominantly resilient at another surface, and a method of manufacturing the armour in which a plurality of sheets of material the compositions of which may vary so far as the ratio of particulate to fibrous material is concerned are stacked together and hot-pressed at a temperature sufficient to cause the matrix material to flow so as to form a unified voidfree composite material the properties of which vary progressively throughout the material from predominantly hard at one surface to predominantly resilient at the opposite surface.

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iaieti H ARMOUR [75] Inventor: Herbert Bowen. North Stoke. England [73']"Assignee: United Kingdom Atomic Energy Authority, London. England 122Filed; Aug. 18. 1972 211 Appl. No.: 281,779

[30] Foreign Application Priority Data Aug. 19. 1971 o'iat Britain3007s/71 [52] US. Cl 109/80, 161/404. 75/206. 89/36 A [SI] Int. Cl. F4lh5/00 [58] Field 6: Search 109/495, 58.5, 79. 80, l09/8l-84; 161/404. 37,38. 170. 193, 194.

[56] References Cited UNITED STATES PATENTS 3.444.033 5/1969 King 161/383.633.520 1/1972 511 11611... 109/112 3.649.342 3/1972 Bartlett...161/404 x 3.68Ll87 8/1972 Bowen l6l/l70 3.684.63l 8/1972 Dunbar...lU9/8l) x 3.69LOUl) 0/1072 Kalnin 161/170 x 3.700.534 10/1972 CookI09/80 X FOREIGN PATENTS 0R APPLICATIONS l'.l40.84l l2/l962 Germany89/36 A I.08l.464 -8/1967 '(ircat Britain ..l Nil/404 PrimaryEraminerDennis L. Taylor Attorney, Agenr. or I 'irmLarson, Taylor &Hinds 71 ABSTRACT I An armour comprising a composite material consistingof a mixture of hard particulate material and fibrous 1 materialdispersed throughout a matrix material the distribution of theparticulate and fibrous materials through the matrix material being suchthat the propmanufacturing the amour in which a plurality of sheets ofmaterial the compositions of which may vary so far as the ratio ofparticulate to fibrous material isconcerned are stacked together andhot-pressed at .6.

temperaturesufiicient to cause the matrix material 16 onesurface topredominantly resilient at the opposite surface.

l aemoua The present invention relates to armour and more specificallyto armour incorporating ceramic materials.

An effective type of armour has a hard surface layer which is backed bya more resilient material. In use the ,hard surface is made to face thedirection from which projectiles are anticipated. The hard surface layeracts to break up any projectiles hitting the annour and the moreresilient backing material absorbs the resulting fragments oftheprojectiles and the front surface layer,

should it be shattered, together with the energy of impact of theprojectiles. For some purposes such as the protection of aeroplanes andpersonnel, Weight is an important consideration, and for these purposesceramic materials are preferred for the hard layer because suchmaterials are both hard and of low density compared with the steels usedto form conventional armour plate. At present, ceramic based'a'rmour ismade great that delamination can occur. v it is an object of the presentinvention to provide an improved armour.

According to thetpresent invention there ,is provided an armourcomprising a composite' material consisting of a mixture of hard.particulate material and fibrous material dispersed throughout a'matrixmaterial. the distribution of t particulate and fibrous materialsthrough the matrix material being such thatthe proper, ties of thecomposite material change progressively from predominantlyhard at onesurface to predom'h nantly resilient at anotherj surl'ace. The mostconvenient way ofachieving a progressive. change in properties is toprepare a pluralityofsheets 40 of material. the compositions ofwhicl'tvary so faras the of a single phase ceramic layer to which is adhesivelybonded a backing layer made of a fibre reinforced plastics material.However, such armour has proved to be not entirely satisfactorybecausethe differences in the physical properties of the two types of materialare so ratioof particulate to fibrous materials is concerned, to

stack-the sheets and then to hot press them at a temperature sufficientto cause the matrix material to flow. so

as to form a unified void-free composite material. the

properties of which vary progressively throughout the material frompredominantly hard at ones'urfacc to. v predominantly resilient atanother surface.

ln a preferred form of. the invention, the particulate Suitable ceramicmaterials are silicon carbide, boron carbide, and silicon nitride. Theglass matrix material may he a cornmonglass. low melting point solderingglass, at how-silicate glass, or a nucleating glass. The fi-, brousmaterial may be a ceramic material inwhisker Tom whiskers of metaloxides such as aluminium or magnum. carbon fibres or even metal wires,if it is destrctl to impart ameasure of ductility into the characiLfllltjN pf the armour. if ceramic whiskers are used..

these can he the sameas the ceramicparticles. but in any event theceramic materials already mentio'nedare suitable. The fibrous and matrixmaterials should be so chosen that the thermal coefficiertts ofeitp'ars'ion are as nearly as possible the same-.lllesirahly the same criteriashould :tlso'zrppiy to the particulate material but it is not =nimportant Particularly suitable glasses or'the ma trix material are thehorn-silicate glass. known by tile material is a ceramic and the. matrixmaterial is a glass.

trade name Pyrex which has the following composition:

wliv

Silica 80.2 '4

Boron oxide 12.3 I w/w Alumina 2.6 'l \vlw Cttlcia O.l "I w/w SodiumOxide 4.5 a w/w Potassium oxide 0 and the nucleating glass known by thetrade name C orning type 9608 which has the following composition:

Silicon dioxide wlw.

69.5 '4 Alumina I 17.8 '4 w/w' 5 Magnesia. 2.8 'Z w/w Lithium oxide 2.5v/w Titania 4.75'71 wlw Zirconia i 0.25% w/w Zine oxide L07! w/w Sodiumoxide l 0.4 it ,w/w Arsenic trioxide 1.0 9? w/w companying'drawing.

' A sheet (if-armour embodying the invention consists of a plurality oflayers 1 of material each of which consists of a mixture. of ceramicparticles 2 andscarbon 1 fibres 3 embedded in a glass matrix-4 which iscontinu- "ous throughout the thickness of the armour, thusbiriding theindividual layers 1 into a single body; The rela tive proportion ofceramic-particles 2 tocarbon fibres Sin each layer 1 varies throughoutthethickness of. the armour so as to provide a graduated changefrornhardnessatjone surface (a higher proportion-of particles litoughness at the opposite surface (a higher proportion" r that;

The sheet of armour can be made byfsta'ckinglio-n gether a pluralityofsheets of material each of which consists of an appropriate mixture ofceramic particle carbon fibres.'a glass binderin powder form and a temethyl ethylketdnmand hot pressing the sheets togcther-at a temperatureand, pressure sufficient-to cause- 'the glass'binder to' flowto; form avoid-free matrtx'" 5 throughout which-are dispersed the hard-particlesand the carbon fibres. The temporary binder-is burnt out during thehot-pressing operation Many types of glass can be used thechoicedepending on a number of factors such as'tlte manufacturing techniquesused or the use towhich thearmour is to be practicable, and also a highfluidity. On. the other hand the physical properties of the finalcomposite'material are dependent upontltose of the glass. it maytherefore I be advisable to. choose a born-silicate glass such as thathaving the composition:

Silica.

tto .t'q n 6t) llomn undo I: *i one Alumina 2.0% iv'a (alcln -l.ll "6it? Sodium oxide 8 l 5 wt Potassium midt- 1 "lulu g which has acoefficient of thermal eitpans on close to t that of carbonfibres.Alternhtivelyii the armor istn be usedin nrduous eondltions itmay he tlesirahleio choose a glass which ham high stir-truth andhardness An embodiment of the invention will nowbe deg scribed, by wayof example. with reference to the ac porary' binder such as' polyvinylacetate dissolved in put. For example.for .hot pressing it isdcsirableQthat' the glass should have the lowestrheltin'g point which ist s t a a at elevated temperatures such as a nucleated glass. for hasbeen impregnated with slurry, excem slurry isre. example. that which hasthe following composition: I moved by means of further rollers. and thetape ts dried before being wound onto rollers. The composition of thesheets 'can be controlled by varying the proportions i ffigl g ig'g Z 5of ceramic particles, glass particles and binder solution Magnesia 21a 1w/w v in the slurry. This method of forming the green" #F' W" g-g xsheets of material .isparticuarly suited to producing a w compositematerial containing straight, well aligned fi y? s 8; 7 fibres. thusmaktng the maximum use of the properties iriisx iec n) a in? it) Of thefibres. lttis also poss ble to'makethe properties I of the armourdirectional in its properties or isotropic In both cases, thetemperature and pressures at which a y a g ing h fi r in successivesheets or th: the hot pressing is carried out are determined by the Casey physical properties of the glass. in addition. care must n practicethe final armour may include sheets of be taken to ensure that thefibres are not damaged durmaterial a y b lh' f t fl q Q Q us ing thefirst method is more appropriate-to themanufac- To achieve, the extr h dr i d by h ture of those sheets containing a high proportion of cc;

sheets which are. to form the hard front surface of the ramic particles,and vice versa. w armour. the mixture from which the appropriate sheetsi claim: l I are made must contain a high proportion of the hard E. Anarmour comprising a composite ptater'ialcon: ceramic particles, and toachieve thishigh density steps sisting of amixture of hard particulatematerial and fiha e to be taken to ensure proper packing of the partirbrous material dispersedthroughout a matrixjmaterlal, E This can be doneby using particles which have a the distribution ofthe particulate andfibrous materials range of discrete dimensions such that the smallerparthrough the matrix material being such that the'propen' ticlcs fitinto the voids between the larger ones. The ties of thecompositematerial change progressively proper particle sizes and the relativevolume proporfrom predominantly hard at one surface to predomitionsrequired to achieve given packing densities are nantly resilient atanother urfacerecorded in the literature for a variety of particle 2. Anarmour according to claim I wherein the rn'a-' shapes. The mixcontaining the proper sizes and protrirt material is a glass.

portions of hard particles, together with just sufficient 3. An armouraccording to claim 2 wherein theglas s volume of glass powder to fillthe residual porosity of is selected from the group comprisingnucleating v I the hard particles is made up with a suitable binder toglasses and borosilicate glasses.

, form a slurry. The slurry is fed under a doctor blade on 4. An armouraccording to claim 1 wherein the pairto a' moving carrier as describedin our co-pending Britticulate material is a ceramic material. H ishapplication No. l6047/68, but in the present case, '5. An armouraccording to claim 4 wherein the cecithcr the carrier or the slurry ismechanically agitated" Y ramic material is selected from the groupcomprising in the region of the deposition of the sheet so as to siliconcarbide. boron carbide and silicon nitride. cause thevarious sizes ofparticles to adopt the dense 6. An armour according to claim l whereinthe lipacking desired. The agitation may be achieved either brousmaterial is carbon fibre. I i I by positioning an ultrasonic transducerwithin a trough 40 r 7. An armour according to claim l wherein the lithrough which the slurry flows or by supporting the brous material is acerainic'materialin whisker form.

moving carrier at the point of emergence of the slurry 8. An armouraccording to claim l wherein the Ftl'rom the doctor blade upon avibrating plate or table. brous material is a'metal oxide in whiskerform. The hardness of subsequent sheets is reduced by dea 9. An armouraccording toclaim I wherein the licreasing the proportion of hardparticles and by in 5 brous material is metal wires. creasing theproportion of'glass binder accordingly. 1 10. A method ofmanufacturingan armour. as

- 25 has already beendescribed. The fibres can be 'scpaing together aplurality ol'shcets of composite material rate and stirred into theslurry. or a tow of fibres can having'dil'fering proportions oliparticulate andfibrous he passed through the slurry and under the doctormaterials dispersed in the matrix material in such a blade. manner thatthe relative proportions of particulate and An alternative way of makingthe sheets. which is fibrous materials vary throughout the stack. andhot particularly suitable for those sheets in which there is pressing ata temperature sufficient to cause'thc matrix to be a higher proportionof fibres. is to pass a continu-- material to flow so as to form aunified void-tree cotnous tow of carbon fibres througha series ofspreading $5 posite material the properties of which varyf'proigres andby increasing the proportionof reinforcing fibresclaimed in claim 3comprising the operationsof stacb rollers so as to spread the fibresinto a tape. and then? sively throughout the material from predominantlyto pass the tape through a bath of a slurry of the be hard at onesurface to predominantly-resilient at run ramic and glass particles. inaddition further slurry can other surface, 7 be sprayed onto thesurfaces ol'the tape. Alter the-tape a

2. An armour according to claim 1 wherein the matrix material is aglass.
 3. An armour according to claim 2 wherein the glass is selectedfrom the group comprising nucleating glasses and borosilicate glasses.4. An armour according to claim 1 wherein the particulate material is aceramic material.
 5. An armour according to claim 4 wherein the ceramicmaterial is selected from the group comprising silicon carbide, boroncarbide and silicon nitride.
 6. An armour according to claim 1 whereinthe fibrous material is carbon fibre.
 7. An armour according to claim 1wherein the fibrous material is a ceramic material in whisker form. 8.An armour according to claim 1 wherein the fibrous material is a metaloxide in whisker form.
 9. An armour according to claim 1 wherein thefibrous material is metal wires.
 10. A method of manufacturing an armouras claimed in claim 1 comprising the operations of stacking together aplurality of sheets of composite material having differing proportionsof particulate and fibrous materials dispersed in the matrix material insuch a manner that the relative proportions of particulate and fibrousmaterials vary throughout the stack, and hot pressing at a temperaturesufficient to cause the matrix material to flow so as to form a unifiedvoid-free composite material the properties of which vary progressivelythroughout the material from predominantly hard at one surface topredominantly resilient at another surface.